The ability to adhere to each other is one of the most fundamental cellular functions necessary for the formation of all metazoans. The most significant histological manifestation of epithelial tumor is the focal loss of normal tissue architecture. Maintenance of normal tissue organization is one of the primary functions of cell-cell adhesion structures and intercellular adhesion is often abnormal in epithelial cancer. Our laboratory is concentrating on understanding the normal and pathological function of cell-cell adhesion protein alphaE(epithelial)-catenin. AlphaE-catenin is often downregulated in a variety of human epithelial tumors: however, the significance of this downregulation and overall mechanisms of alpha-catenin in tissue homeostasis and cancer is not well understood. To understand the significance of alpha-catenin downregulation in human cancer, we model these events in mice using conditional gene knockout technology. These and other approaches resulted in realization that alpha-catenin plays an important role in regulation of self-renewal an differentiation of stem cells and the genetic loss of alpha-catenin in stem cell compartment can result in prominent defects in tissue homeostasis and development of cancer. In this proposal we will study the molecular mechanisms of alpha-catenin in signal transduction and use genetic loss-of-function and pharmacological inhibition experiments to explore the novel therapeutic interventions for the treatment of epithelial tumors displaying a decrease or loss of alpha-catenin expression.